Two-stroke internal combustion engines in recreational vehicles are typically liquid-cooled or air-cooled. Sometimes, in an air-cooled two-stroke engines, the exhaust side of the engine is positioned facing the front of the vehicle such that the hot exhaust side of the engine faces into the wind and is provided with the maximum amount of air flow. The intake side of the engine is typically cooler than the exhaust side since the intake port of the engine is exposed to the relatively cool fuel-air mixture entering the combustion chamber. For this reason, the cooling of the intake side of the engine has been considered unnecessary. In an air-cooled two-stroke engine, the intake side of the engine can face the rear of the vehicle and therefore has no direct airflow. Nonetheless, relatively small indirect airflow actually reaches the intake side of the engine and it has always been considered adequate since a large portion of the heat generated in the combustion chamber is carried outside the engine by the exhaust gases through the exhaust port and/or transferred to the cylinder head and the exhaust side of the cylinder.
In a liquid-cooled two-stroke engine, cooling fluid is circulated into the cylinder block and cylinder head through a cooling circuit. A water pump, usually positioned on the exhaust side of the engine, pumps cooling fluid under pressure into the crankcase of the engine and the cooling fluid circulates upward through a cylinder jacket at least partially surrounding the cylinder(s) and through passageways in the cylinder head before exiting the engine through a water outlet typically equipped with a thermostat. The now hot cooling fluid is delivered to a radiator which cools the cooling fluid before routing it back into the engine in a continuous cycle.
However, conventional cooling circuit for two-stroke engine may adversely affect the performance of the engine by cooling only portions of the engine. Areas of the engine may not be adequately cooled inducing distortions of the cylinder block which can shorten the life of the engine and reduce its performance. Also, critical components of the engine, such as bearings, may not be adequately cooled which can also shorten the life of the engine and reduce its performance.
Thus, there is a need for a cooling circuit for a two-stroke engine that alleviates some of the drawbacks of prior cooling circuits and preferably improves the performance and reliability of the two-stroke engine.